ADP2380-EVALZ Analog Devices, ADP2380-EVALZ Datasheet - Page 15

• Manufacturer Part Number: ADP2380-EVALZ
• Description: Power Management IC Development Tools 20V 4A Evaluation Board
• Manufacturer: Analog Devices
• Type: DC/DC Converters, Regulators & Controllersr
• Series: ADP2380r

Specifications of ADP2380-EVALZ

• Rohs: yes
• Tool Is For Evaluation Of: ADP2380
• Input Voltage: 4.5 V to 20 V
• Factory Pack Quantity: 1

Data Sheet
APPLICATIONS INFORMATION
INPUT CAPACITOR SELECTION
The input decoupling capacitor is used to attenuate high
frequency noise on the input. This capacitor should be a
ceramic capacitor in the range of 10 µF to 47 µF. Place the
capacitor close to the PVIN pin. The loop composed of this
input capacitor, high-side NFET, and low-side NFET must be
kept as small as possible.
The voltage rating of the input capacitor must be greater than
the maximum input voltage. The rms current rating of the input
capacitor should be larger than the following equation:
OUTPUT VOLTAGE SETTING
The output voltage of
resistive divider using the following equation:
To limit output voltage accuracy degradation due to FB bias
current (0.1 µA maximum) to less than 0.5% (maximum),
ensure that R
Table 6 lists the recommended resistor divider values for
various output voltage options.
Table 6. Resistor Divider for Different Output Voltages
V
1.0
1.2
1.5
1.8
2.5
3.3
5.0
VOLTAGE CONVERSION LIMITATIONS
The minimum output voltage for a given input voltage and
switching frequency is constrained by the minimum on time.
The minimum on time of the
minimum output voltage at a given input voltage and frequency
can be calculated using the following equation:
where:
V
t
f
R
R
I
R
MIN_ON
SW
OUT_MIN
OUT
DSON_HS
DSON_LS
L
OUT_MIN
is the series resistance of the output inductor.
is the switching frequency.
(V)
V
I
V
I
OUT_MIN
C
OUT_MIN
OUT
is the minimum on time.
IN
is the minimum output current.
is the low-side MOSFET on resistance.
is the high-side MOSFET on resistance.
is the minimum output voltage.
_
RMS
=
× t
0
= V
BOT
6 .
=
MIN_ON
I
×
R
10
10
15
20
47.5
10
22
IN
is less than 30 kΩ.
OUT
TOP




× t
1
, ±1% (kΩ)
+
MIN_ON
× f
×
ADP2380
R
R
SW
TOP
BOT
D
− (R
× f
×




1 (
SW
ADP2380
DSON_LS
−
can be set by an external
− (R
D
)
DSON_HS
+ R
is typically 120 ns. The
L
R
15
10
10
10
15
2.21
3
) × I
BOT
− R
, ±1% (kΩ)
OUT_MIN
DSON_LS
) ×
Rev. 0 | Page 15 of 28
(1)
The maximum output voltage for a given input voltage and
switching frequency is constrained by the minimum off time
and the maximum duty cycle. The minimum off time is typically
200 ns, and the maximum duty cycle of the
typically 90%.
The maximum output voltage limited by the minimum off time
at a given input voltage and frequency can be calculated using
the following equation:
where:
V
t
I
The maximum output voltage, limited by the maximum duty
cycle at a given input voltage, can be calculated by using the
following equation:
where D
As Equation 1 to Equation 3 show, reducing the switching
frequency alleviates the minimum on time and minimum off
time limitation.
INDUCTOR SELECTION
The inductor value is determined by the operating frequency,
input voltage, output voltage, and inductor ripple current. Using
a small inductor leads to a faster transient response but degrades
efficiency, due to larger inductor ripple current; whereas, using
a large inductor value leads to smaller ripple current and better
efficiency but results in a slower transient response.
As a guideline, the inductor ripple current, ΔI
to 1/3 of the maximum load current. The inductor can be
calculated using the following equation:
where:
V
V
ΔI
f
D is the duty cycle.
The
loop to prevent subharmonic oscillations when the duty cycle
is larger than 50%. The internal slope compensation limits the
minimum inductor value.
MIN_OFF
SW
OUT_MAX
OUT_MAX
IN
OUT
V
I
L
OUT_MAX
is the switching frequency.
is the input voltage.
is the inductor current ripple.
OUT_MAX
ADP2380
V
L
is the output voltage.
D =
OUT_MAX
is the minimum off time.
=
is the maximum output current.
MAX
is the maximum output voltage.
(
V
V
V
× (1 − t
∆
OUT
= V
IN
is the maximum duty.
IN
I
L
= D
−
uses adaptive slope compensation in the current
×
IN
V
f
× (1 − t
MAX
OUT
MIN_OFF
SW
× V
)
×
MIN_OFF
× f
D
IN
SW
) − (R
× f
SW
DSON_LS
) − (R
DSON_HS
+ R
ADP2380
L
L
) × I
, is typically set
− R
ADP2380
OUT_MAX
DSON_LS
is
) ×
(2)
(3)